Providers of television-based entertainment are attempting to expand the range of services that they offer to subscribers in order to increase revenues. In addition to television content such as that found on conventional cable networks, some providers also offer interactive video services, such as video on demand. The provision of interactive video services is stimulating the further development of digital network technology, which in turn will enable providers to increase the number and kinds of video services offered to subscribers.
Video on demand allows users to select and watch video content over a network as part of an interactive television experience. Video on demand systems may support “streaming,” in which digital video content is available to the subscriber while the video streams over the network, and/or “downloading,” in which digital video content is downloaded to a subscriber device, such as a set-top box, before the content is available to the subscriber.
Some digital video networks that provide video on demand services stream digital video content to clients via multicasting and unicasting, where multicasting is used to distribute the same content to multiple clients concurrently and unicasting is used to provide specific content to a particular client. The clients receive streams of digital video content via multicasting or unicasting and playout the digital video content to a device such as a television. Although a particular client may only playout one stream at a time, there are instances in which it is desirable to have more than one unicast stream active at the same time between a stream server and the client. In conventional digital video networks, the establishment of multiple unicast streams between a stream server and a client triggers the setup of multiple unicast sessions between the stream server and the client to reserve the bandwidth resources that are needed to support each different unicast stream. However, if the client is only playing out one unicast stream at a time, valuable network resources can be wasted using this technique.